This invention relates generally to improvements in fuel cell fuel delivery arrangements for use in combustion tools, and more specifically to actuating the fuel cell metering valve for delivering the appropriate amount of fuel for use by a combustion tool during the driving of fasteners, as well as associated combustion tools and their components.
As exemplified in Nikolich U.S. Pat. Nos. 4,403,722, 4,483,474, 4,522,162, and 5,115,944, all of which are incorporated by reference, it is known to use a dispenser such as a fuel cell to dispense a hydrocarbon fuel to a combustion tool, also known as a combustion gas-powered tool or combustion nailer, such as, for example, a combustion gas-powered fastener-driving tool. Such fastener-driving tools and such fuel cells are available commercially from ITW-Paslode (a division of Illinois Tool Works, Inc.) of Vernon Hills, Ill., under its IMPULSE trademark. In particular, a fuel cell of this type is described in Nikolich U.S. Pat. No. 5,115,944, listed above.
One design criterion associated with the use of such fuel cells, which contain separate compartments of pressurized fuel and propellant, is the prevention of leakage of one or both of the above constituents. The objective is to prevent or minimize leakage after production and before use, also known as shelf life, and also during periods when the fuel cell is installed in the tool but the tool is stored or otherwise not in use. To address this design criterion, fuel metering valves have been used to sealingly maintain the fuel inside the fuel cell until the tool is actuated.
Another design criterion of such fuel cells is that only a desired amount of fuel should be emitted by the fuel cell for each combustion event, depending on the temperature and altitude where the tool is operated. The amount of fuel should be carefully monitored to provide the desired combustion, yet in a fuel-efficient manner to prolong the working life of the fuel cell. Prior attempts to address this dosage factor have resulted in fuel metering valves attached to the fuel cell (U.S. Pat. No. 6,302,297), or located in the fuel cell (U.S. Pat. No. 5,263,439) both of which are also incorporated by reference.
A further design consideration of such fuel cells is that emission of the fuel, and therefore actuation of the tool, should be responsive to the user. In present combustion nailers with conventional fuel delivery systems, the end user must exert approximately fourteen pounds of force to actuate the tool. This amount of required actuation force can cause fatigue and strain on the user, especially after extended use.
Accordingly, there is a need for an improved combustion tool that uses a fuel cell that allows for variable fuel dosages.
There is also a need for an improved combustion tool that requires relatively less actuation force by the end user.